Changing pix configs when failover is configured

just started working for a different company. They have redundant pix

The question is if I changing the config on one pix do i also have to make the same change on another? I would think you would have to because what would happen if the configs differed and one went down. I would think in that case the failover pix would only run what it was configured to and any changes not applied to it would be programmed.

here is the long version and why the change is being made:

They have decided to change internet carriers due to the divide between

Verizon and Level 3. Because of the divide they would have lost their current public ip subnet and found cheaper service through a company called global crossing which means they are also changing ip addresses.

Here is the question: I believe I know the answer already but I just wanted to check and make sure I am not wrong.

Do I need to change the config on both pix's to reflect the public IP address change?

Thanks,

Steve